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Northeast Cold Water Fish Habitat Vulnerability Assessment

Species that depend on cold-water river habitat are vulnerable to warming from climate change, but just how vulnerable? Lingering uncertainties about the relationship between changing air and water temperatures, the capacities of different fish species to adapt to exposure, and the ways climate change will affect other environmental stressors like diseases, make it difficult to predict. In order to make informed decisions about protecting fish habitat, resource managers must understand the degree of the threat. This review offers a comprehensive overview of what is known, what remains uncertain, and what measures that can be taken now to reduce the future impacts of warming on cold water fish habitat.

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Final Report: Climate Change and Riverine Cold Water Fish Habitat in the Northeast

Additional Resources

This report is associated with a project that completed three assessments of the vulnerability of terrestrial, aquatic, and coastal habitats (ecosystems) to climate change, including sea level rise. One assessment evaluated 13 terrestrial and wetland habitat types, the second [this report] evaluated cold water stream habitats, and the third evaluated coastal habitats.

Technical description

If we are to anticipate and mitigate the potential impacts of climate change on organisms and their habitats it is vital that we understand their relative vulnerabilities. In this analysis, we attempt to estimate the likely vulnerability to climate change of riverine habitat for cold water fish in the Northeast. These fish are recreationally, economically, and culturally important species that also can be viewed as indicators for the entire riverine cold water ecosystem.

As historical context, much of the riverine cold water fish habitat in the Northeast has been lost due to anthropogenic stressors, particularly habitat destruction and reduced access to spawning areas by the installation of dams. This has been most marked in the southern part of the habitat’s range in the northeastern states, where losses may be as high as 50%. Climate change confronts this habitat with a new and important stressor. As air temperatures continue to warm, waterways may also warm beyond the physiological tolerances of cold water fish such as brook trout, brown trout, and other salmonids. Also, the projected increased frequency and severity of extreme events (floods and droughts, for example) may pose significant risks to this habitat type.

Applying a vulnerability assessment framework, in this review we consider the exposure, sensitivity, and adaptive capacity of cold water fish. The main conclusion of this review is that riverine cold water fish habitat in the Northeast is indeed vulnerable to climate change, but may not be as vulnerable as earlier studies may have suggested. Most habitat loss due to warming in the Northeast may occur in the southern part of the habitat’s range (for example, Virginia and West Virginia) and at lower elevations (for example, coastal plain cold water streams from Massachusetts north into Maine). Further north and at higher elevations, riverine cold water fish habitat is likely to persist for substantially longer than earlier studies had suggested.

The review also discusses continuing scientific uncertainties as well as mitigation measures that can be taken to reduce the impacts of warming on cold water fish habitat.